Fixing device and image forming apparatus having a slantingly extended irradiation area

ABSTRACT

A fixing device includes: a conveying unit that conveys a recording material with an image formed thereon toward a predetermined conveying direction so as to cross a fixing area where the image is heated to be fixed; a laser light source that has an irradiation area as the fixing area slantingly extending relative to a predetermined image arrangement reference direction along a width direction of the recording material crossing the conveying direction of the recording material, and irradiates the irradiation area with laser light; and a reflecting member that is provided so as to surround the irradiation area and has a reflecting face that reflects reflected light from the irradiation area so that the irradiation area is again irradiated with the reflected light.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application No. 2010-213782 filed on Sep. 24, 2010.

BACKGROUND Technical Field

This invention relates to a fixing device and an image forming apparatusincluding the fixing device.

SUMMARY

According to an aspect of the invention, there is provided a fixingdevice including: a conveying unit that conveys a recording materialwith an image formed thereon toward a predetermined conveying directionso as to cross a fixing area where the image is heated to be fixed; alaser light source that has an irradiation area as the fixing areaslantingly extending relative to a predetermined image arrangementreference direction along a width direction of the recording materialcrossing the conveying direction of the recording material, andirradiates the irradiation area with laser light; and a reflectingmember that is provided so as to surround the irradiation area and has areflecting face that reflects reflected light from the irradiation areaso that the irradiation area is again irradiated with the reflectedlight.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described indetail based on the following figures, wherein:

FIGS. 1A and 1B are schematic representations to show a fixing deviceaccording to an embodiment of the invention; FIG. 1A is a perspectiveview and FIG. 1B is a drawing seen from B direction of FIG. 1A;

FIG. 2 is a schematic representation to show the relationship between animage and an irradiation area;

FIG. 3 is a schematic representation to show a state when a thick lineimage is fixed to the irradiation area;

FIG. 4 is a schematic representation to show an outline of the generalconfiguration of an image forming apparatus according to Embodiment 1 ofthe invention;

FIG. 5 is a schematic representation to show a fixing device ofEmbodiment 1 of the invention;

FIG. 6 is a schematic representation when the fixing device ofEmbodiment 1 of the invention is seen from a cross-sectional directionthereof;

FIG. 7 is a schematic representation to show a fixing device as a firstmodified example of Embodiment 1 of the invention;

FIG. 8 is a schematic representation to show a fixing device as a secondmodified example of Embodiment 1 of the invention;

FIG. 9 is a schematic representation to show a fixing device as a thirdmodified example of Embodiment 1 of the invention;

FIG. 10 is a schematic representation to show an outline of a fixingdevice of Embodiment 2 of the invention;

FIG. 11 is a schematic representation to show an outline of an imageforming apparatus incorporating a fixing device of Embodiment 3 of theinvention;

FIG. 12 is a schematic representation to show an outline of the fixingdevice of Embodiment 3 of the invention;

FIGS. 13A and 13B are schematic representations to show an outline of afixing device of Embodiment 4 of the invention;

FIG. 14 is a flowchart to show a control flow of Embodiment 4 of theinvention;

FIGS. 15A and 15B are schematic representations to show a fixing deviceas a modified example of Embodiment 4 of the invention;

FIG. 16 is a schematic representation to show a state of an evaluationimage in Example 1;

FIG. 17 is a graph to show the result of Embodiment 1; and

FIG. 18 is a graph to show the result of Embodiment 2.

DETAILED DESCRIPTION Summary of Exemplary Embodiments of the Invention

First, a summary of an embodiment of a fixing device incorporating theinvention will be discussed.

FIGS. 1A and 18 are schematic representations to show a fixing deviceaccording to an embodiment of the invention; FIG. 1A is a perspectiveview and FIG. 1B is a drawing seen from B direction of FIG. 1A.

The fixing device includes a conveying unit 2 for conveying a recordingmaterial 1 with an image formed thereon toward a predetermined conveyingdirection so as to cross a fixing area where an image can be heated andfixed, a laser light source 3 having an irradiation area IR as a fixingarea slantingly extending relative to a predetermined image arrangementreference direction along the width direction of the recording material1 crossing the conveying direction of the recording material 1, thelaser light source 3 for irradiating the irradiation area IR with laserlight Li, and a reflecting member 4 provided so as to surround thenarrow width direction of the irradiation area IR and having areflecting face 4 a for reflecting reflected light Lr so that theirradiation area IR is again irradiated with the reflected light Lr fromthe irradiation area IR by the laser light Li applied from the laserlight source 3.

As a representative material for forming an image on the recordingmaterial 1, toner used with electrophotography can be named, but thematerial is not limited to the toner; for example, ink of heat andfusion type used with an ink jet system, etc., may be adopted.

As the recording material 1, representatively, continuous forms paper(roll paper), a cut sheet of paper can be named, but a film medium otherthan the paper medium may be adopted.

Further, the expression “predetermined image arrangement referencedirection along the width direction of the recording material 1 is usedto mean that an image is mainly arranged along the width direction ofthe recording material 1, and also contains a ruled line, etc.

As a representative form of the laser light source 3, array laser typewherein a plurality of light emission parts of the laser light Li areprovided in a row along the extending direction of the irradiation areaIR.

Preferably, the irradiation area IR is provided linearly along thedirection crossing the recording material 1, but may be shaped likeseparated lines or a mountain. Further, the reflected light Lr from theirradiation area IR also contains scattered light.

Light reflected by the reflecting member 4 and again applied to theirradiation area IR may be again applied to a part containing theirradiation area IR and is not limited the irradiation area. For thereflecting member, the reflecting face 4 a may be, for example, a bentmirror face, a retroreflective face, or a diffusing surface. Further,the reflecting member 4 may be of an integral structure or may be of asplit structure. For example, for the split structure, at least eitherthe upstream side or the downstream side in the conveying direction ofthe recording material 1 from the laser light source 3 may be furthersplit; the reflecting member may have a structure capable of againirradiating the irradiation area with the reflected light Lr from theirradiation area IR.

The back of the recording material 1 may be provided with an opposedmember placed so as to hold the recording material 1 toward the laserlight source 3 and transmitted light of the laser light Li passingthrough the recording material 1 may be reflected on the opposed member(flat or curved surface member) or another bent reflecting member (backside reflecting member 5 described later) may be provided at a distantposition from the recording material 1. Alternatively, nothing may beprovided.

Next, the function in the irradiation area IR in the embodiment will bediscussed.

FIG. 2 is a drawing to show the relationship between an image IMG (animage with image density 100% is assumed) formed linearly along thewidth direction of the recording material 1 crossing the conveyingdirection of the recording material 1 as an image and the irradiationarea IR and to compare with an irradiation area IR′ of a generalirradiation area. In this case, the irradiation area IR in the exampleis inclined by inclination angle θ from the width direction of therecording material 1; while, the irradiation area IR′ in a comparisonexample is provided along the width direction of the recording material1. It is assumed that the width of the image IMG (length along theconveying direction of the recording material 1) is larger than thewidth of the irradiation area IR, IR′.

When the recording material 1 is conveyed in such a state, motion of theimage IMG relative to the irradiation area IR at the irradiation timeand the fixing degree of the image IMG become as shown in FIG. 3.

In the drawing, in the example, since the irradiation area IR isinclined relative to the image IMG, a portion where the image IMG doesnot exist in the surrounding of the image IMG passing through theirradiation area IR and the image IMG is again irradiated with thereflected light Lr from the portion, whereby fixing of the image IMG ispromoted.

On the other hand, in the comparison example, at the stage at which theimage IMG is applied to the irradiation area IR′, the image IMG is againirradiated with the reflected light Lr from the portion where the imageIMG does not exist, whereby fixing of the image IMG is promoted.However, the reflected light Lr is not used at the stage at which theimage IMG covers the irradiation area IR′, and fixing of the image IMGremains in an insufficient state. When the trailing end of the image IMGenters the irradiation area IR′, the image is again irradiated with thereflected light Lr, whereby fixing of the image IMG is promoted.

Thus, in the fixing degree in the conveying direction of the recordingmaterial 1 of the image IMG (corresponding to the width direction of theimage IMG), in the example, insufficiency of fixing of the centerportion relative to the width direction of the image IMG is minimized;whereas, in the comparison example, fixing of the center portionrelative to the width direction of the image IMG becomes insufficient.Therefore, as compared with the example, it is necessary to enlargelaser output at the fixing time in the comparison example.

Generally, as an image on the recording material 1, an image along thewidth direction of the recording material 1 is often adopted. It becomesnoticeable, for example, when a thick ruled line is used, particularlywhen a Gothic thick character is used, etc. Therefore, the irradiationarea IR of the laser light Li is inclined relative to the widthdirection of the recording material 1, whereby it is made possible tofix an image stably with small power consumption.

As shown in FIG. 2, if the inclination angle θ of the irradiation areaIR is made large to some extent, the use efficiency of the reflectedlight Lr when the image IMG is fixed increases. However, if theinclination angle θ is made large, the length of the irradiation area IRastride the recording material 1 becomes long. For example, in the arraylaser type wherein a plurality of high-output semiconductor lasers areused as the laser light source 3, there are disadvantages of the costand power consumption as the number of semiconductor lasers increases.Therefore, preferably the inclination angle θ is set in a small range tosome extent.

As shown in FIG. 1B, from the viewpoint of effective use of transmittedlight of the laser light Li applied to the recording material 1, in theform wherein an opposed member coming in contact with the back of therecording material 1 is not included, preferably the fixing devicefurther includes the back side reflecting member 5 provided in a partopposed to the reflecting member across the recording material 1 forreflecting the transmitted light so that the transmitted light appliedfrom the laser light source 3 and passing through the recording material1 is again applied to the back part of the recording material 1corresponding to the irradiation area IR.

Further, from the viewpoint of adopting a simple configuration as thereflecting member 4, preferably the reflecting face 4 a of thereflecting member 4 opposed to the recording material 1 has acylindrically curved surface. The shape on a different side from thereflecting face 4 a of the reflecting member 4 is not limited, butpreferably the shape is a shape similar to the reflecting face 4 a fromthe viewpoint of more simplifying the configuration of the reflectingmember 4. Further, preferably the back side reflecting member 5 is of asimilar shape to that of the reflecting member 4 and has a cylindricallycurved surface relative to the back part corresponding to theirradiation area IR.

From the viewpoint of effectively accomplishing the reflectingperformance on the reflecting member 4, preferably the laser lightsource 3 is placed at a position where the laser light Li is applied tothe irradiation area IR from an inclined position along thecylindrically curved surface of the reflecting member 4 from thedirection orthogonal to the recording material 1 face in the irradiationarea IR. Accordingly, the reflecting member 4 in a part againirradiating the irradiation area IR with the reflected light Lr of thelaser light Li applied from the laser light source 3 is ensured largelyand stable re-irradiation is performed.

Further, from the viewpoint of ensuring the reflecting performance onthe reflecting member over a long term, preferably the fixing deviceincludes a protection member 6 for allowing the laser light Li to passthrough and preventing an evaporated substance evaporated from the imageon the recording material 1 from being deposited on the reflecting face4 a of the reflecting member 4. The protection member 6 may be provideddirectly on the reflection member 4 or may be provided separately fromthe reflection member 4. An evaporated substance from the recordingmaterial 1 is also contained in addition to the evaporated substancefrom the image.

From the viewpoint of performing fixing more fitted to the image on therecording material 1, preferably the fixing device includes adetermination unit for determining whether or not the image densityalong the extending direction of the irradiation area exceeds apredetermined criterion value from image information of a predeterminedimage length in the conveying direction of the recording material 1 andan irradiation area changing unit, if the image density exceeds thecriterion value based on the determination result of the determinationunit, the means for finding an extending direction of a new irradiationarea IR wherein the image density in an inclined direction relative tothe width direction of the recording material 1 and a differentdirection from the extending direction of the irradiation area IR doesnot exceed the criterion value and changing the irradiation area so thatthe irradiation area IR becomes the new irradiation area.

That is, if the image density in the direction along the initially setupirradiation area IR becomes higher than the criterion value, theinclination angle θ is changed and the image density in the directionalong the new irradiation area IR whose inclination angle θ is changedis prevented from exceeding the criterion value, whereby sufficientfixing performance is ensured without increasing power consumption.

The predetermined image length in the conveying direction of therecording material 1 may be for each image or may be every two or moreimages. The irradiation area changing unit may move the laser lightsource 3 and the reflecting member 4 so that the irradiation area ischanged and, for example, if the recording material 1 is a cut sheet,the means may change the conveying direction of the recording material1.

To apply such a fixing device to an image forming apparatus, an imageforming section for forming an image on the recording material 1 and afixing device for fixing an image formed on the image material 1 in theimage forming section may be included and the fixing device describedabove may be used as the fixing device.

In such an image forming apparatus, preferably, the recording material 1continuous along the conveying direction is used as the recordingmaterial 1 to be used.

Next, the invention will be discussed in more detail based onembodiments shown in the accompanying drawings.

Exemplary Embodiment 1

FIG. 4 is a schematic representation to show the general configurationof an image forming apparatus according to Embodiment 1 incorporatingthe fixing device of the embodiment described above.

The image forming apparatus of the embodiment uses a recording materialP shaped like continuous forms paper as a recording material and is madeup of an image forming main body device 10A for forming an image on therecording material P and a supply device 10B for supplying the recordingmaterial P and a storage device for storing the recording material Pwith an image formed thereon on both sides of the image forming mainbody device 10A. The recording material P may be shaped like a roll ormay be shaped like a fold, for example. In the embodiment, the recordingmaterial P is shaped like a roll.

The image forming main body device 10A of the embodiment useselectrophotography, for example, and is made up of color image formingsections 20 for forming toner images of multiple colors using toners offour colors, for example, on the recording material P (specifically, ayellow image forming section 20Y, a magenta image forming section 20M, acyan image forming section 20C, and a black image forming section 20K),a fixing device 40 for fixing toner images formed in a multiplex stateon the recording material P in the color image forming sections 20, anda plurality of roll members 16 to 19 provided as required, and the like.

The roll member 16 is a position adjustment roll for performing positionadjustment when the recording material P is introduced to the imageforming section 20, the roll member 17 is a stretch roll for introducingthe recording material P toward the fixing device 40, and the rollmembers 18 and 19 are tension giving rolls for giving tension asrequired when the recording material P with a fixed image is conveyedtoward the storage device 10C.

The color image forming sections 20 have each a roughly similarconfiguration except for used toner and therefore the black imageforming section 20K is taken as a representative example in thedescription. The black image forming section 20K has a cylindricalphotoconductive drum 21 having a photoconductive layer (not shown) on asurface and rotating in an arrow E direction. The photoconductive drum21 is surrounded by a charging device 22 for charging thephotoconductive layer of the photoconductive drum 21 to a predeterminedpotential, an exposure device 23 for selectively irradiating thephotoconductive layer charged by the charging device 22 with laserlight, for example, to form an electrostatic latent image on thephotoconductive drum 21, a developing device 24 for developing theelectrostatic latent image formed by the exposure device 23 in toner toform a visible image, a transfer device 25 for transferring the tonerimage on the photoconductive drum 21 onto the recording material P, acleaner 26 for cleaning the remaining toner on the photoconductive drum21 after the transfer, and the like.

The arrangement of the toner colors of the image forming sections 20 isnot limited to the arrangement described above and any other arrangementmay be used, needless to say.

The supply device 10B is made up of a supply roll 12 for holding therecording material P wound around a core like a roll, tension givingrolls 14 and 15 for giving tension while conveying the recordingmaterial P to the image forming main body device 10A for supply, and thelike. On the other hand, the storage device 10C is made up of a windingroll 13 for winding the recording material P around a core for storageand the like.

In the image forming apparatus, each color toner image is transferred tothe recording material P supplied from the supply device 10B in eachcolor image forming section 20 of the image forming main body device 10Aand the toner images are multiplexed on the recording material P. Therecording material P to which the unfixed multiplexed toner image istransferred is fixed in the fixing device 40 and then is wound andstored in the storage device 10C.

Next, the fixing device 40 in the image forming apparatus will bediscussed based on FIG.

In the figure, the fixing device 40 of the embodiment includes an arraylaser 41 as a laser light source for irradiating an irradiation area IRextending linearly on the recording material P with laser light Li, asemi-cylindrical reflecting area having a reflecting face provided so asto surround the irradiation area IR for reflecting reflected light sothat reflected light from the irradiation area IR by laser light Liapplied from the array laser 41 is again applied toward the irradiationarea IR, and a semi-cylindrical back side reflecting member 43 opposedto the reflecting member 42 across the recording material P forreflecting transmitted light so that transmitted light applied from thearray laser 41 and passing through the recording material P is againapplied toward a back side part of the recording material P.

In the embodiment, the fixing device includes a support mechanism 50 forsupporting the array laser 41, the reflecting member 42, and the backside reflecting member 43 so that the irradiation area IR is inclinedrelative to the width direction of the recording material P. That is, inthe embodiment, the irradiation area IR is placed in an inclinationdirection from the width direction of the recording material P(direction indicated by x-x in the figure).

In the example, the array laser 41 uses five high-output semiconductorlasers, but the number of semiconductor lasers, etc., is not limited andany number may be included; however, the array laser needs a lengthcapable of covering the image width in the width direction of therecording material P. The array laser 41 contains an optical system forfocusing the laser light Li to the irradiation area IR on the recordingmaterial P, for example. The laser light beams Li from the adjacenthigh-output semiconductor lasers overlap each other in end parts,whereby the irradiation strengths of the laser light beams Li along theextension direction of the irradiation area IR become roughly equal toeach other.

The reflecting member 42 is provided with an opening 42 a of a long holeto allow the irradiation area IR to be irradiated with the laser lightLi from the array laser 41 in a roughly central portion of thesemi-cylinder.

The support mechanism 50 of the embodiment is made up of a rectangularsupport body 51 for fixing and supporting the array laser 41, supportedpiece 52 provided on both sides of the reflecting member 42 along thewidth direction of the recording material P, a supported piece 53provided on the back side reflecting member 43, and a subframe 54 forsupporting the support body 51 and the two supported pieces 52 and 53.The subframe 54 is provided with fit holes 54 a to 54 c into which thesupport body 51 and the two supported pieces 52 and 53 are fitted. Thesupport body 51 and the two supported pieces 52 and 53 are inserted intothe fit holes 54 a to 54 c respectively, whereby the array laser 41, thereflecting member 42, and the back side reflecting member 43 are fixedand supported in one body. Only one subframe 54 is shown, but a similarsubframe 54 (not shown) is also provided on the opposite side along thewidth direction of the recording material P, needless to say.

Further, the subframes 54 are fixed to, for example, a main frame (notshown) of the image forming main body device 10A, whereby theirradiation area IR is set in an inclination direction from the widthdirection of the recording material P. The angle between the widthdirection of the recording material P (direction indicated by x-x in thefigure) and the extension direction of the irradiation area is shown asinclination angle θ in the figure.

FIG. 6 shows a cross section when the fixing device 40 of the embodimentis seen from a lateral direction. The irradiation area IR is inclinedrelative to the width direction of the recording material P, needless tosay.

In the figure, the laser light Li applied from the array laser 41proceeds from the opening 42 a of the reflecting member 42 to theirradiation area IR on the recording material P. The reflected light Lrof the laser light Li applied to the irradiation area from theirradiation area IR is reflected on the reflecting face 42 b of thereflecting member 42 and is again applied to the irradiation area IR.

On the other hand, transmitted light Lt of the laser light Li passingthrough the recording material P is again applied to the partcorresponding to the irradiation area IR on the back side of therecording material P by the reflecting face 43 b of the back sidereflecting member 43.

In the embodiment, the irradiation area IR is set in the inclinationdirection relative to the wide direction of the recording material P,namely, is inclined by the inclination angle θ (see FIG. 5) relative tothe width direction of the recording material P. Thus, if a line image(for example, a ruled line, etc.,) along the width direction of therecording material P exists, the image density (area coverage) of animage relative to the irradiation area IR lessens and sufficientreflected light Lr is used.

Therefore, as compared with the case where the irradiation area isprovided along the width direction of the recording material P, when thesame line image is fixed, laser output is decreased and the image isfixed with low power consumption.

In the embodiment, the back side reflecting member 43 is provided, butno back side reflecting member 43 may be provided. In this case, itbecomes necessary to a little increase laser output as compared with thecase where the back side reflecting member 43 is provided.

FIG. 7 shows a modified example of the fixing device 40 of theembodiment. Unlike the fixing device in FIG. 6, protection members 44and 45 provided opposed to the recording material P are attached to thereflection member 42 and the back side reflecting member 43.

The protection members 44 and 45 are formed of a material allowing thelaser light Li to pass through. Attenuation for the laser light Li, thereflected light Lr, and the transmitted Lt is small, the light can beeffectively used, and heat resistance at the fixing time is alsoincluded.

Usually, in a system wherein toner on the recording material is heatedand fused for fixing an image, when the toner is heated and fused, anadditive, etc., of the toner is evaporated and if the evaporatedsubstance is deposited on the reflecting face 42 b of the reflectingmember 42, for example, degradation of the reflection efficiency on thereflecting face 42 b is incurred. When the recording material is alsoheated, moisture is evaporated, etc., and the reflection efficiency onthe reflecting face 42 b is still more degraded because of the moisture.Similar comments also apply to the back side reflecting member 43.

In such a case, the protection members 44 and 45 are provided, wherebythe reflection efficiency on the reflecting face 42 b of the reflectingmember 42 and that on the reflecting face 43 b of the back sidereflecting member 43 are maintained and the fixing efficiency ismaintained in a stable state. The evaporated substance is also depositedon the protection members 44 and 45, but may be cleaned as required;attenuation of the laser light Li caused by deposition of the evaporatedsubstance on the protection members 44 and 45 is very small and theeffect is small as compared with a decrease in the reflection efficiencyon the reflection faces 42 b and 43 b.

Here, the protection members 44 and 45 are provided directly for thereflection member 42 and the back side reflecting member 43, but may beprovided separately from the reflection member 42 and the back sidereflecting member 43.

Further, FIG. 8 shows a second modified example of the embodiment; theposition of the opening 42 a of the reflecting member 42 differs.

In the example, the opening 42 a of the reflecting member 42 is providedat a position to the downstream side in the conveying direction of therecording material P along the reflecting face 42 b.

Such placement is adopted, whereby the reflected light Lr from theirradiation area IR by the laser light Li from the array laser 41 ismuch reflected toward the upstream side in the conveying direction ofthe recording material P from the opening 42 a of the reflecting member42. However, the wide reflecting face 42 b exists in the part and thusthe reflected light Lr is easily again applied to the irradiation areaIR. Thus, the fixing efficiency is improved.

The transmitted light Lt does not increase on the upstream side ascompared with the reflected light Lr and thus a difference does not muchoccur.

In the embodiment described above, the reflecting member 42 is of theintegral type, but may be of a separate type; for example, thereflecting member may be separated in the portion of the opening 42 a.Further, the reflection member is separated into parts in thecross-sectional direction and has a plurality of members different inthe distance from the irradiation area so that the reflecting face 42 bis separated into parts. In this case, particularly residence of air onthe reflecting face 42 b of the reflecting member 42 is suppressed, anevaporated substance from toner, etc., becomes hard to remain, and dirtoccurrence on the reflecting face 42 b is suppressed.

Similar comments also apply to the back side reflecting member 43.

In the embodiment, the array laser 41 is provided at a distant positionfrom the recording material P as compared with the reflecting member 42.However, for example, the array laser 41 is brought close to therecording material P and may be caused to apply the laser light Li fromthe same position as the reflecting face 42 b of the reflecting member42. Further, the array laser 41 may be placed inside the reflectingmember 42 (recording material P side from the reflecting face 42 b).

In the embodiment, continuous forms paper is used as the recordingmaterial P, but cut sheets may be used. In this case, for example, aguide mechanism for guiding the recording material P toward the fixingdevice 40 and a conveying mechanism for conveying the recording materialP may be provided separately.

In the embodiment, as the fixing device 40, after the irradiation areaIR is irradiated with the laser light Li by the array laser, naturalcooling is performed. However, a press member for pressing the recordingmaterial P so as to catch it in the press member may be provideddownstream in the conveying direction of the recording material P in theirradiation area IR and the recording material P may be cooled in thepress member. In this case, a semi-fused image heated in the irradiationarea IR is pressed by the press member, whereby glossiness of the imageis improved.

Further, in the embodiment, the number of irradiation areas IR is one,but a plurality of array lasers 41 may be provided relative to theconveying direction of the recording material P, for example.

FIG. 9 shows a third modified example of the embodiment. One reflectingmember 42 is provided with two openings 42 a along the conveyingdirection of the recording material P and laser light Li beams from thetwo array laser 41 (41A and 41B) are applied from the openings 42 a,whereby two irradiation areas IR (IRA and IRB) are formed.

The reflecting member 42 has two cylindrically curved surfaces arrangedside by side and the back side irradiation area 43 also has a similarconfiguration.

In the configuration, first the laser light Li is applied to the imageon the recording material P in the irradiation area IRA by the upstreamarray laser 41A and after a lapse of one time, further the laser lightLi is applied in the irradiation area IRB by the downstream array laser41B.

When the laser light is thus applied, the interface temperature betweenthe toner and the recording material P a little rises in the upstreamirradiation area IRA in a portion where the image density is high on therecording material P (for example, solid image portion). Then, althoughthe interface temperature gradually falls in the portion where no laserlight is applied, as the image density is high, the surface area issmall, the heat discharge is small, and temperature lowering issuppressed in a small amount.

Next, heating is again performed in the downstream irradiation area IRB,whereby the interface temperature also rises sufficiently and sufficientadherence is ensured.

On the other hand, the interface temperature once rises sufficiently inthe portion where the image density is low (for example, highlight imageportion), but lowers rapidly. Heating is again performed in thedownstream irradiation area IRB and the interface temperature againrises. That is, the interface temperature is kept by twice applyinglaser light in the portion where the image density is high; while, theinterface temperature is kept by once applying laser light in theportion where the image density is low. This is repeated.

Therefore, sufficient adherence is ensured regardless of the imagedensity on the recording material P.

When such two irradiation areas IR are included, the following may beperformed:

Laser output in the upstream irradiation area IRA is made smaller thanlaser output in the downstream irradiation area IRB and accordingly theirradiation area length along the conveying direction of the recordingmaterial P is made long, whereby the irradiation time in the downstreamirradiation area IRB prolongs. At this time, the irradiation strengthand the irradiation area length for enabling an image to be sufficientlyheated and fused in the upstream irradiation area IRA are providedconforming to the portion where the image density is high, needless tosay.

When such irradiation is performed, in the portion where the imagedensity is high, sufficient adherence is ensured in the upstreamirradiation area IRA and if the downstream irradiation area IRB isirradiated with light for a short time, no problem arises. On the otherhand, in the portion where the image density is low, as the contact areabetween the toner particles and the outside air is wide in irradiationof the upstream irradiation area IRA with light, heat discharge growsand toner is not sufficiently heated or fused. However, the irradiationstrength is enhanced in the downstream irradiation area IRB and thussufficient fusing is accomplished and adherence is ensured. This meansthat sufficient heating and fusing of toner are accomplishedindependently of the image density on the recording material P.

In the modified example, the irradiation area IR is also inclinedrelative to the width direction of the recording material P, needless tosay.

Here, the two irradiation areas IRA and IRB are placed in parallel; ifthey are placed a little in unparallel, laser output can be lessened ascompared with the form in which the irradiation area is provided in thewidth direction of the recording material P.

Exemplary Embodiment 2

FIG. 10 is a schematic representation to show an outline of a fixingdevice 40 of Embodiment 2 of the invention.

The fixing device 40 of the embodiment differs from the fixing device 40of Embodiment 1 (for example, see FIG. 5) in that it has no back sidereflecting member. Components similar to those of Embodiment 1 aredenoted by similar reference numerals and will not be discussed again indetail.

In the figure, the fixing device 40 has an opposed member 46 placed soas to hold a recording material P toward an array laser 41 at a positionopposed to a reflecting member 42 across the recording material P. Theopposed member 46 is shaped like a white and heat-resistant round barhaving a surface subjected to low friction treatment using fluorocarbonresin, etc., for example, and the axial direction is placed conformingto an extension direction of an irradiation area IR. Therefore, therecording material P skewing on the opposed member 46 is conveyed moresmoothly.

In the described fixing device 40, the recording material P is conveyedwhile always sliding on the opposed member 46, so that flopping of therecording material P in the irradiation area IR is also suppressed andlaser output in the irradiation area is easily made uniformed.

Using the opposed member 46, the irradiation area IR is irradiated withlaser light Li and transmitted light passing through the recordingmaterial P is reflected by the surface of the opposed member 46. Thus,if no back side reflecting member is included, reflected light from thetransmitted light is again applied to the proximity of the irradiationarea IR and fixing efficiency is improved.

The opposed member 46 is not limited to the round bar shape and may beshaped like a flat plate, for example, and may have a size capable offorming the irradiation area IR. The opposed member 46 may be a metalmember if it has heat resistance; preferably, the opposed member 46 hassmall heat conductivity so as not to release heating.

Further, in the embodiment, the laser light Li is applied to theirradiation area IR from a roughly orthogonal direction, but may beapplied from a slant direction, for example, as shown in FIG. 8.

Exemplary Embodiment 3

FIG. 11 shows an outline of an image forming apparatus incorporating afixing device 40 of Embodiment 3 of the invention. The image formingapparatus of the embodiment differs from the image forming apparatus ofEmbodiment 1 (see FIG. 4) in that a cut recording material is used as arecording material. Components similar to those of Embodiment 1 aredenoted by similar reference numerals and will not be discussed again indetail.

In the figure, the image forming apparatus uses electrophotography, forexample, and is made up of color image forming sections 20 for formingmultiple-color toner image using toners of four colors, for example, ona recording material (shaped like a cut sheet) P (specifically, a blackimage forming section 20K, a cyan image forming section 20C, a magentaimage forming section 20M, and a yellow image forming section 20Y), abelt-like intermediate transfer body 30 for conveying color toner imagesformed in the color image forming sections 20 in a multiplex state, abatch transfer device (secondary transfer device) 66 for collectivelytransferring the multiplexed toner images on the intermediate transferbody 30 to the recording material P, for example, the fixing device 40for fixing unfixed toner image transferred onto the recording material Pin the secondary transfer device 66, and the like.

The color image forming sections 20 have each a roughly similarconfiguration except for used toner and are configured like the imageforming sections 20 of Embodiment 1 (see FIG. 4) and therefore will notbe discussed again in detail.

The intermediate transfer body 30 of Embodiment 3 is stretched onstretch rolls 31 to 36. For example, the stretch roll 31 is rotated as adrive roll and the stretch roll 34 is rotated as the tension roll.

The secondary transfer device 66 is placed with the stretch roll 35 as abackup roll. A belt cleaner 37 for cleaning remaining toner on theintermediate transfer body 30 is provided at a position opposed to thestretch roll 31 across the intermediate transfer body 30.

Further, a recording material storage section for storing a recordingmaterial P is provided below the intermediate transfer body 30 in theimage forming apparatus. In a conveying path of the recording material Pconveyed from the recording material storage section 62, a plurality ofconveying rolls 63 to 65 are provided from the recording materialstorage section 62 to the secondary transfer device 66 and a conveyingbelt 67 for conveying the recording material P subjected to thesecondary transfer to the fixing device 40 and a discharge roll 68 fordischarging the recording material P with an image fixed by the fixingdevice 40 to the outside of the apparatus are provided.

Thus, in the embodiment, in each color image forming section 20, eachcolor toner image formed on a photoconductive drum 21 rotating in an Fdirection in the figure is transferred onto the intermediate transferbody 30 in a transfer device (primary transfer device) 25, wherebymultiplexed toner image is formed on the intermediate transfer body 30.On the other hand, the recording material P is conveyed to a secondarytransfer position by the conveying rolls 63 to 65 from the recordingmaterial storage section 62 and the toner image multiplexed on theintermediate transfer body 30 is collectively transferred onto therecording material P in the secondary transfer device 66. The recordingmaterial P to which the multiplexed toner image is collectivelytransferred in the secondary transfer device 66 is conveyed on theconveying belt 67 and the image on the recording material P is fixed inthe fixing device 40. The recording material P with the image fixed isdischarged to the outside of the image forming apparatus by thedischarge roll 68.

FIG. 12 shows an outline of the fixing device 40 in the embodiment. Anattraction conveying device 47 of electrostatic attraction type, forexample, for holding and conveying the recording material P is providedat a position opposed to the reflecting member 42 across the recordsheet P.

The attraction conveying device 47 is made up of two roll members 47 band 47 c, a belt member 47 a stretched between the two roll members 47 band 47 c and circulating, and a charging member 47 d for charging thebelt member 47 a.

In the fixing device 40 of the embodiment, when the recording material Pto which an unfixed toner image is transferred arrives at the fixingdevice 40, the belt member 47 a of the attraction conveying device 47 ischarged by the charging member 47 d and thus the recording material P iselectrostatically attracted to the belt member 47 a and is conveyed withrotation of the belt member 47 a. The recording material P conveyed byrotation of the belt member 47 a is irradiated with laser light Li froman array laser 41 in an irradiation area IR and then is further conveyeddownstream with rotation of the belt member 47 a. A peeling member foreasily peeling the recording material P with the image fixed from theattraction conveying device 47 is provided, whereby the recordingmaterial P is easily peeled from the belt member 47 a. The array laser41 and the reflecting member 42 are placed inclinedly relative to thewidth direction of the recording material P conveyed by the attractionconveying device 47, needless to say.

In the embodiment, the attraction conveying device 47 is used, wherebyif the recording material P is a cut sheet, the attitude of therecording material P in the irradiation area IR is kept stable and theirradiation strength with the laser light Li in the irradiation area IRis also made uniform. Preferably, the belt member 47 a used with theattraction conveying device 47 has a surface capable of reflectingtransmitted light passing through the recording material P by the laserlight Li in the irradiation area IR on the back side of the recordingmaterial P; for example, a white-based pigment may be added.

Here, the charging member 47 d comes in contact with the belt member 47a; for example, a corona charger, etc., may be used to charge the beltmember 47 a in a distant state from the belt member 47 a. The attractionconveying device 47 electrostatically attracts the recording material P,but the recording material P may be air-sucked from the back side of thebelt member 47 a. Further, the belt member 47 a is stretched between thetwo roll members 47 b and 47 c; however, for example, an opposed member(for example, roll member) may be provided corresponding to theirradiation area IR and the vicinity of the irradiation area may beprojected toward the array laser 41.

Exemplary Embodiment 4

Embodiment 4 of the invention differs from Embodiments 1 to 3 in thatthe inclination angle of an irradiation area IR relative to the widthdirection of a recording material in a fixing device 40 is variablyadjusted. The used recording material may be continuous forms paper or acut sheet and therefore in the description to follow, the type ofrecording material is not limited.

FIG. 13A shows an outline of a configuration when the fixing device 40in the embodiment is seen from a surface of a recording material P andFIG. 13B is an enlarged view of a part of FIG. 13A.

In the figure, the fixing device 40 of the embodiment has a supportmechanism 50 for supporting an array laser 41, a reflecting member 42,etc., and the array laser 41 and the reflecting member 42 are supportedon subframes 54 provided in both end parts along the width direction ofthe recording material P. In the embodiment, a rock shaft 55 extendingin a direction roughly orthogonal to the recording material face isfixedly provided on one subframe 54 and a support rod 56 extending in adirection along the recording material face is attached to the othersubframe 54.

Further, in the embodiment, the fixing device has a move mechanism 70for moving the support rod 56 along the move direction of the recordingmaterial P with the rock shaft 55 as the rock center. The move mechanism70 bears a role of irradiation area changing unit.

The move mechanism 70 of the embodiment is made up of a motor 71, apinion 72 rotated by a rotation shaft 71 a of the motor, a rack 73meshing with the pinion 72, and two guide pins 74 provided on the rack73, and the support rod 56 on the subframe 54 side is sandwiched betweenthe guide pins 74.

Thus, the rack 73 is moved by rotation of the motor 71, wherebyinclination angle θ of the array laser 41, etc., is changed with therock shaft 55 as the rock center. In the embodiment, a controller 100performs change control of the inclination angle θ.

The controller 100 in the embodiment determines whether or not areacoverage (image density) along the inclination angle θ exceeds apredetermined criterion value from image information of a predeterminedimage length in a conveying direction of the recording material P. Ifthe area coverage exceeds the criterion value based on the determinationresult, the controller 100 controls the inclination angle θ so that thearea coverage when new inclination angle θ is set does not exceed thecriterion value.

Thus, the controller 100 of the embodiment controls rotation of themotor 71 according to a flow shown in FIG. 14.

In the figure, first, area coverage at initialized inclination angle θ₀is calculated (S01). Whether or not the calculated value exceeds thecriterion value is determined (S2). If the value does not exceed thecriterion value, the initialized inclination angle θ₀ is maintained asit is, and fixing is performed (S03).

If it is determined at step S02 that the calculated area coverageexceeds the criterion value, the area coverage when the inclinationangle θ₀ is set to (θ₀+2.5°) is calculated (S04). Whether or not theinclination angle θ at this time exceeds preset maximum value isdetermined (S05). If the angle does not exceed the maximum value,further whether or not the angle exceeds the criterion value isdetermined (S06). If the angle does not exceed the criterion value, themotor 71 is rotated so that the angle is set to the inclination angle θat this time (S08).

If the angle exceeds the criterion value, the inclination angle θ isfurther incremented by 2.5° (S07) and the process returns to step S04.

On the other hand, if it is determined at step S05 that the inclinationangle θ exceeds the maximum value, the inclination angle θ is set to(θ₀−2.5°) and new area coverage is calculated (S09). At this time,whether or not the inclination angle θ falls below the minimum value isdetermined (S10). If the angle does not fall below the minimum value,whether or not the area coverage exceeds the criterion value isdetermined (S11). If the area coverage does not exceed the criterionvalue, the motor 71 is rotated so that the angle is set to theinclination angle θ at this time (S13).

If it is determined at step S11 that the angle exceeds the criterionvalue, the inclination angle θ is further decremented by 2.5° (S12) andthe process returns to step S09.

Further, if it is determined at step S10 that the inclination angle θfalls below the minimum value, it is determined that setting of theinclination angle θ is inappropriate, a warning is reported to anoperator (S14).

The fixing device 40 of the embodiment calculates the state of an imagein area coverage along the inclination angle θ per image, therebystabilizing the fixing efficiency at the fixing time. Thus, the areacoverage along the inclination angle θ is suppressed, the reflectedlight on the recording material P is effectively used, and fixing isperformed efficiently.

In the embodiment, the inclination angle θ is incremented or decrementedby 2.5°, but the embodiment is not limited to it; any angle may beadopted. Although the move mechanism 70 using the rack and the pinion isshown, any other known system may be applied needless to say.

FIGS. 15A and 15B show a modified example of the embodiment. In theembodiment, the inclination angle θ on the array laser 41 side ischanged; in the modified example, in a mode wherein the recordingmaterial is a cut sheet, the move direction of a recording material P ischanged in response to the area coverage.

In FIG. 15A, the recording material P is conveyed while it is guided byguide members 80 (80 a and 80 b) for guiding the width direction of therecording material before arriving at an irradiation area. The guidemembers 80 have rock shafts 81 (81 a and 81 b) so that the guide members80 can rock in roughly central portions, and the two guide members canrock together by a mechanism (not shown).

In the described fixing device 40, in a mode wherein an image on therecording material P is fixed at the inclination angle θ in a state inFIG. 15A, if it is determined that the area coverage exceeds a criterionvalue, the guide members 80 are rocked without changing the inclinationangle θ, whereby the conveying direction of the recording material P ischanged by angle α as in FIG. 15B and in the irradiation area with thearray laser 41, the inclination angle θ from the width direction of therecording material P substantially becomes (θ−α) in the example. Theconveying direction of the recording material P is thus changed, wherebyit is made possible to set the area coverage to an appropriate range.

When the conveying direction of the recording material P in the fixingdevice 40 is thus changed, image formation is scarcely affected andtherefore an obstacle does not occur.

The foregoing description of the embodiments of the present inventionhas been provided for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise forms disclosed. Obviously, many modifications and variationswill be apparent to practitioners skilled in the art. The embodimentswere chosen and described in order to best explain the principles of theinvention and its practical applications, thereby enabling othersskilled in the art to understand the invention for various embodimentsand with the various modifications as are suited to the particular usecontemplated. It is intended that the scope of the invention defined bythe following claims and their equivalents.

EXAMPLES Example 1

In Example 1, an experiment is conducted to check the relationshipbetween area coverage and fixing property. An array laser and areflection member are used and an irradiation area is provided along thewidth direction of a recording material without inclining theirradiation area.

FIG. 16 shows a state of an evaluation image at the experiment time, anda 100% solid image and 60% and 20% halftone images are used.

Evaluation of the fixing property is measured according to the followingindex (crease value):

As the crease value in the example, a post-fixed image is once foldedand is opened and a broken image portion is lightly wiped with cottonand the image width of the portion where the image is lost is evaluatedin a numeric value. In the example, if the crease value is 60 or less,it is assumed that fixing has no substantial problem.

As a result, as shown in FIG. 17, minimum necessary laser output forfixing an image (corresponding to power consumption) depends largely onthe area coverage. For example, if the case where the crease value is 60is assumed, to fix an image with area coverage about 20%, laser outputof about 0.55 J/cm² is sufficient; while, laser output of 0.8 J/cm² isrequired for the solid image. In this case, the laser output at thefixing time must be set to 0.8 J/cm² or more and it is understood thatlarge power is fruitlessly consumed particularly for an image with smallarea coverage.

Example 2

In Example 2, a fixing device has an array laser and a reflecting member(except aback side reflecting member) and area coverage when theinclination angle of an irradiation area is changed for each line imageextending in the width direction of a recording material.

In the example, a beam width is set to 1.5 mm, a recording materialwidth is set to 500 mm, and seven levels of the line width of each lineimage (the length along the move direction of the recording material)are selected out of the range of 1 to 50 mm.

As a result, as shown in FIG. 18, the value of the area coverage for anirradiation area rapidly lowers as the inclination angle increases; thistendency is noticeable when the line width is 10 mm or less. Theirradiation area is inclined relative to the width direction of therecording material, whereby the area coverage lessens and if the linewidth is thick, the area coverage lessens.

In the example, when the line width is 50 mm, if the inclination angleis set to 10′, the area coverage becomes 60% or less.

Referring to FIG. 17 of the result in Example 1, the following isunderstood: When the line width is 50 mm, if the inclination angle isset to 0°, laser output of about 0.8 J/cm² is required; if theinclination angle is set to 10°, similar fixing is performed with laseroutput of about 0.7 J/cm². If the line width becomes narrow, thetendency further increases; for example, when the line width is 10 mm,the inclination angle is set to about 2°, a similar effect is provided.

Further, it is also understood that, for example, when the line width is5 mm, if the inclination angle is set to 3°, the area coverage becomesabout 20% and thus laser output may be about 0.55 J/cm².

As described above, it is understood that the inclination angle in theirradiation area largely contributes to the magnitude of laser outputand by extension, lower power consumption.

What is claimed is:
 1. A fixing device comprising: a conveying unit thatconveys a recording material with an image formed thereon toward apredetermined conveying direction so as to cross a fixing area where theimage is heated to be fixed; a laser light source that has anirradiation area as the fixing area slantingly extending relative to apredetermined image arrangement reference direction along a widthdirection of the recording material crossing the conveying direction ofthe recording material, and irradiates the irradiation area with laserlight; and a reflecting member that is provided so as to surround theirradiation area and has a reflecting face that reflects reflected lightfrom the irradiation area so that the irradiation area is againirradiated with the reflected light.
 2. The fixing device as claimed inclaim 1, further comprising a back side reflecting member that isprovided in a part opposed to the reflecting member across the recordingmaterial and reflects transmitted light reached from the laser lightsource through the recording material to be again reached to a back partof the recording material corresponding to the irradiation area.
 3. Thefixing device as claimed in claim 1, wherein the reflecting face of thereflecting member opposed to the recording material has a cylindricallycurved surface.
 4. The fixing device as claimed in claim 2, wherein thereflecting face of the reflecting member opposed to the recordingmaterial has a cylindrically curved surface.
 5. The fixing device asclaimed in claim 3, wherein the laser light source is provided at aposition where the laser light is reached to the irradiation area froman inclined position along the cylindrically curved surface of thereflecting member from a direction orthogonal to a surface of therecording material in the irradiation area.
 6. The fixing device asclaimed in claim 4, wherein the laser light source is provided at aposition where the laser light is reached to the irradiation area froman inclined position along the cylindrically curved surface of thereflecting member from a direction orthogonal to a surface of therecording material in the irradiation area.
 7. The fixing device asclaimed in claim 1, further comprising a protection member that allowsthe laser light to pass through and prevents a substance evaporated fromthe image on the recording material from being deposited on thereflecting face of the reflecting member.
 8. The fixing device asclaimed in claim 2, further comprising a protection member that allowsthe laser light to pass through and prevents a substance evaporated fromthe image on the recording material from being deposited on thereflecting face of the reflecting member.
 9. The fixing device asclaimed in claim 3, further comprising a protection member that allowsthe laser light to pass through and prevents a substance evaporated fromthe image on the recording material from being deposited on thereflecting face of the reflecting member.
 10. The fixing device asclaimed in claim 4, further comprising a protection member that allowsthe laser light to pass through and prevents a substance evaporated fromthe image on the recording material from being deposited on thereflecting face of the reflecting member.
 11. The fixing device asclaimed in claim 5, further comprising a protection member that allowsthe laser light to pass through and prevents a substance evaporated fromthe image on the recording material from being deposited on thereflecting face of the reflecting member.
 12. The fixing device asclaimed in claim 6, further comprising a protection member that allowsthe laser light to pass through and prevents a substance evaporated fromthe image on the recording material from being deposited on thereflecting face of the reflecting member.
 13. The fixing device asclaimed in claim 1, further comprising: a determination unit thatdetermines whether or not an image density along an extending directionof the irradiation area exceeds a predetermined criterion value fromimage information of a predetermined image length in the conveyingdirection of the recording material; and an irradiation area changingunit that, in case the image density exceeds the criterion value basedon the determination result of the determination unit, finds anextending direction of a new irradiation area wherein an image densityin a slanting direction relative to the width direction of the recordingmaterial and a different direction from the extending direction of theirradiation area does not exceed the criterion value, and changes theirradiation area so that the irradiation area becomes the newirradiation area.
 14. The fixing device as claimed in claim 2, furthercomprising: a determination unit that determines whether or not an imagedensity along an extending direction of the irradiation area exceeds apredetermined criterion value from image information of a predeterminedimage length in the conveying direction of the recording material; andan irradiation area changing unit that, in case the image densityexceeds the criterion value based on the determination result of thedetermination unit, finds an extending direction of a new irradiationarea wherein an image density in a slanting direction relative to thewidth direction of the recording material and a different direction fromthe extending direction of the irradiation area does not exceed thecriterion value, and changes the irradiation area so that theirradiation area becomes the new irradiation area.
 15. The fixing deviceas claimed in claim 3, further comprising: a determination unit thatdetermines whether or not an image density along an extending directionof the irradiation area exceeds a predetermined criterion value fromimage information of a predetermined image length in the conveyingdirection of the recording material; and an irradiation area changingunit that, in case the image density exceeds the criterion value basedon the determination result of the determination unit, finds anextending direction of a new irradiation area wherein an image densityin a slanting direction relative to the width direction of the recordingmaterial and a different direction from the extending direction of theirradiation area does not exceed the criterion value, and changes theirradiation area so that the irradiation area becomes the newirradiation area.
 16. The fixing device as claimed in claim 4, furthercomprising: a determination unit that determines whether or not an imagedensity along an extending direction of the irradiation area exceeds apredetermined criterion value from image information of a predeterminedimage length in the conveying direction of the recording material; andan irradiation area changing unit that, in case the image densityexceeds the criterion value based on the determination result of thedetermination unit, finds an extending direction of a new irradiationarea wherein an image density in a slanting direction relative to thewidth direction of the recording material and a different direction fromthe extending direction of the irradiation area does not exceed thecriterion value, and changes the irradiation area so that theirradiation area becomes the new irradiation area.
 17. The fixing deviceas claimed in claim 5, further comprising: a determination unit thatdetermines whether or not an image density along an extending directionof the irradiation area exceeds a predetermined criterion value fromimage information of a predetermined image length in the conveyingdirection of the recording material; and an irradiation area changingunit that, in case the image density exceeds the criterion value basedon the determination result of the determination unit, finds anextending direction of a new irradiation area wherein an image densityin a slanting direction relative to the width direction of the recordingmaterial and a different direction from the extending direction of theirradiation area does not exceed the criterion value, and changes theirradiation area so that the irradiation area becomes the newirradiation area.
 18. The fixing device as claimed in claim 6, furthercomprising: a determination unit that determines whether or not an imagedensity along an extending direction of the irradiation area exceeds apredetermined criterion value from image information of a predeterminedimage length in the conveying direction of the recording material; andan irradiation area changing unit that, in case the image densityexceeds the criterion value based on the determination result of thedetermination unit, finds an extending direction of a new irradiationarea wherein an image density in a slanting direction relative to thewidth direction of the recording material and a different direction fromthe extending direction of the irradiation area does not exceed thecriterion value, and changes the irradiation area so that theirradiation area becomes the new irradiation area.
 19. An image formingapparatus comprising: an image forming section that forms an image on arecording material; and the fixing device as claimed in claim 1 thatfixes the image formed on the recording material in the image formingsection.
 20. The image forming apparatus as claimed in claim 19, whereinthe recording material is provided to be continuous along the conveyingdirection.
 21. The fixing device as claimed in claim 1, wherein theirradiation area slantingly extends so as to utilize reflected lightfrom a portion of a non-image area.